The invention relates to a hearing prosthesis system using a cochlear implant.
Deafness may be due to total sensorineural hearing loss. This is where the cochlea does not respond to sound waves, and therefore does not generate electrical signals for transmission to the cochleal nerves. An auditory prosthesis may use a suitable stimulation electrode arrangement capable of stimulating the auditory nerves. One current prosthesis design includes an external transmitter and battery, and an internal receiver. The receiver interacts with electrodes that are surgically placed in the cochlea to allow selective stimulation of the cochlear wall (Hochmair et al., U.S. Pat. Nos. 4,284,856 and 4,357,497, incorporated herein by reference). The electrodes are typically contained in a substantially flexible electrode carrier having sufficient stiffness to be guided into the cochlea in the desired coiled shape (Hochmair-Desoyer et al., Annals of the New York Academy of Sciences 405:173-182 (1991), incorporated herein by reference).
FIG. 1 shows a section view of an ear with a typical cochlear implant system. A normal ear transmits sounds through the outer ear 10 to the eardrum 12, which moves the bones of the middle ear 14, which in turn excites the cochlea 16. The cochlea 16 includes an upper channel, known as the scala vestibuli 18, and a lower channel, known as the scala tympani 20, which are connected by the cochlear duct 22. In response to received sounds transmitted by the middle ear 14, the fluid filled scala vestibuli 18 and scala tympani 20 transmit waves, functioning as a transducer to generate electric pulses that are transmitted to the cochlear nerve 24, and ultimately to the brain.
To overcome total sensorineural hearing loss, a cochlear implant system produces direct electrical stimulation of the cochlea 16. A typical system may include an external microphone that provides an audio signal input to a signal processing stage (not shown) where various signal processing schemes can be implemented. For example, signal processing approaches that are well-known in the field of cochlear implants include continuous interleaved sampling (CIS) digital signal processing, channel specific sampling sequences (CSSS) digital signal processing (as described in co-pending U.S. patent application Ser. No. 09/648,68, filed Aug. 25, 2000, and incorporated herein by reference), spectral peak (SPEAK) digital signal processing, and compressed analog (CA) signal processing. Typically, the processed signal is then converted into a digital data format, such as a sequence of data frames, for transmission into an implanted receiver 39.
Besides getting the processed audio information to the implanted receiver 39, existing cochlear implant systems also need to deliver electrical power from outside the body through the skin to satisfy the power requirements of the implanted portion of the system. FIG. 1 shows an arrangement based on inductive coupling through the skin to transfer both the required electrical power and the processed audio information. As shown in FIG. 1, a primary coil 38 (connected to the external signal processor) is externally placed adjacent to a subcutaneous secondary coil 34 (connected to the receiver 39). This arrangement inductively couples a radio frequency (rf) electrical signal to the receiver 39.
The receiver 39 is able to extract both a power component from the rf signal it receives, and the audio information for the implanted portion of the system. Besides extracting the audio information, the receiver 39 also performs additional signal processing such as error correction, pulse formation, etc., and produces a stimulation pattern (based on the extracted audio information) that is sent through connected wires 44 to an implanted electrode carrier 46. Typically, this electrode carrier 46 includes multiple electrodes on its surface that provide selective stimulation of the cochlea 16.
The transmission rf signal for primary coil 38 is typically provided by a prominent behind-the-ear (BTE) module. This BTE module may also contain other system components such as the microphone and the external signal processing arrangement. The BTE module may be quite visually obtrusive, and it is known that some wearers of such devices are very sensitive that their appearance is abnormal.
A representative embodiment of the present device includes a signal processing device for a cochlear implant. The device body fits into the ear canal of a user. The device body includes a microphone, a signal processor, and a transmitter. The microphone converts an acoustic signal present at the device body into a representative electrical signal. The signal processor performs signal processing of the representative electrical signal to form a cochlear implant signal. The transmitter converts the cochlear implant signal into a radio signal for transmission to a cochlear implant.
Another embodiment includes a cochlear implant system that has a signal processor that fits in the ear canal of a user. The signal processor processes an acoustic signal present in the ear of the user to produce a representative radio signal. A separate power transmitter transmits an electrical power signal through the skin of the user. A cochlear implant receives the radio signal and the electrical power signal and produces for the auditory nerve of the user an electrical stimulation signal representative of the acoustic signal.
In further embodiments, the device body may include a mechanical stimulation module that delivers to the inner ear structure of the user a mechanical stimulation signal representative of a portion of the acoustic signal. In such a device the cochlear implant signal is representative of a first subrange of frequencies in the acoustic signal, and the mechanical stimulation signal is representative of a second subrange of frequencies in the acoustic signal.
The processing performed by the signal processor may include at least one of compression, beamforming, and filtering. The signal processing may be continuous interleaved sampling (CIS) digital signal processing, channel specific sampling sequences (CSSS) digital signal processing, spectral peak (SPEAK) digital signal processing, or compressed analog (CA) signal processing.
An implanted battery module may power the cochlear implant, and the battery module may be rechargeable responsive to the transmitted electrical power signal.
The cochlear implant may use extracochlear electrodes to deliver the electrical stimulation signal. Alternatively, cochleostomy window associated electrodes may deliver the electrical stimulation signal. Or, multi-channel array electrodes may be partially or fully inserted into the cochlea of the user to deliver the electrical stimulation signal.
Another embodiment includes a cochlear implant system having a power transmitter that transmits an electrical power signal through the skin of the user, and a cochlear implant. The cochlear implant includes (i) a battery module that powers the cochlear implant, and that is rechargeable responsive to the transmitted electrical power signal, and (ii) a signal processor including a microphone. The signal processor processes an acoustic signal present in the ear of the user, and produces for the auditory nerve of the user an electrical stimulation signal representative of the acoustic signal.